**Molecular dynamics algorithms for path integrals at constant pressure**

GJ Martyna and A Hughes and ME Tuckerman, JOURNAL OF CHEMICAL PHYSICS, 110, 3275-3290 (1999).

DOI: 10.1063/1.478193

Extended system path integral molecular dynamics algorithms have been
developed that can generate efficiently averages in the quantum
mechanical canonical ensemble **M. E. Tuckerman, B. J. Berne, G. J.
Martyna, and M. L. Klein, J. Chem. Phys. 99, 2796 (1993)**. Here, the
corresponding extended system path integral molecular dynamics
algorithms appropriate to the quantum mechanical isothermal-isobaric
ensembles with isotropic-only and full system cell fluctuations are
presented. The former ensemble is employed to study fluid systems which
do not support shear modes while the latter is employed to study solid
systems. The algorithms are constructed by deriving appropriate
dynamical equations of motions and developing reversible multiple time
step algorithms to integrate the equations numerically. Effective
parallelization schemes for distributed memory computers are presented.
The new numerical methods are tested on model (a particle in a periodic
potential) and realistic (liquid and solid para-hydrogen and liquid
butane) systems. In addition, the methodology is extended to treat the
path integral centroid dynamics scheme, **J. Cao and G. A. Voth, J. Chem.
Phys. 99, 10070 (1993)**, a novel method which is capable of generating
semiclassical approximations to quantum mechanical time correlation
functions. (C) 1999 American Institute of Physics.
**S0021-9606(99)50906-9**.

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